1. Field of the Invention
The present invention relates generally to belt-driven transportation systems, and particularly to such systems configured as lift assemblies and conveyor assemblies.
2. Description of the Related Art
Transportation systems such as lift assemblies are well known for moving items or people between two vertically differing locations. Transportation systems such as conveyor assemblies are well known for moving items or people between two horizontally differing locations. It is also known to move the platform or carriage of these systems through a belt-driven apparatus.
One well-known and useful type of lift assembly is the scissor-type, which moves between a lowered or contracted state, and an elevated or extended state as its load-supporting platform is moved between differing vertical locations. Such lift assemblies are commonly driven through hydraulic cylinders, screw-drive mechanisms or expandable pneumatic bladder arrangements, and some prior types of scissor lift assemblies are belt-driven. These prior lift assemblies, however, often require a substantial amount of power, particularly when moving from their lowermost contracted states, or are difficult to reliably, precisely control.
Further, some prior belt-driven transportation systems can be problematic to install or repair, and sometimes to operate, due to the belt being moved out of its guided position along its designed path over pulleys that it engages. Another problem with some types of belt-driven transportation systems is that they rely on traction between the belt and the pulleys to operate, which can lead to slippage under heavy loading and result in unintentional lift collapse. Additionally, some transportation systems of the types described above, particularly lift assemblies, undesirably require operating space that cannot be easily accommodated or interferes with carrying out the operation to which the system is applied. For example, some prior lift assemblies have platform heights in their fully contracted states that require the load to first be lifted a substantial vertical distance from the level of a floor, on which the base is positioned, to place it on the platform. Thus, it would be preferable to minimize the height of the platform in its fully contracted or lowered state.
A transportation system configured as a lift assembly or conveyor assembly that addresses at least one of the above-mentioned problems is desirable.